Bipartisanship, on any issue of consequence, does not exist as a force in the universe. Proximately, it’s because Republicans know that the benefit they’re deriving in the short term far exceeds the criticism they’re getting from the political elite. One reason is that the party’s base, egged on by the Tea Party movement, encourages and rewards their behavior. There are many other reasons — congressional Democrats aren’t entirely blameless — but Ron Brownstein, James Fallows and President Obama have all offered persuasive theories. Add to that mass migration of Americans to the sunbelt, immigration, the ability of outside interests to enforce party conformity, a campaign finance system that rewards self-interest, and archaic Senate rules — well, bipartisanship is dead. The entire Republican Senate conference voting against a deficit reduction commission that many of them had previously endorsed? Surprised, David Broder? How can you blame that on liberals? You can’t.